There is a problem with setting an artificial price and taxing up to it: Government’s addiction to money streams.

For axample, let’s suppose the Federal government taxed the difference between real gas prices and $3/gallon. This year they might be raking in 80 cents per gallon. However, if the real price goes up to $2.80 next year, their windfall would be only a quarter of the prior year’s. You know they already spent the 80 cents in next year’s budget. So now they have to tax something else to address the shortfall.